[PATCH] D119261: [DependenceAnalysis][PR52170] Conservative crash on overflowed loop backedge

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

In D119261#3345920 <https://reviews.llvm.org/D119261#3345920>, @bmahjour wrote:

> I'm generally in favour of this patch, but just not sure if there is (or should be) a guarantee that SCEV will NOT produce an AddRec in overflow situations. For example when a GEP has the inbounds attribute, the produced address after adding the index/offset cannot cause an unsigned overflow, so not sure why SCEV would produce different results depending on whether the index/offset could wrap! SCEV seems to produce an AddRec for the offset/index (eg. `%i.add`) regardless whether it could wrap or not. It's just the GEP that seems to be behaving the way you described.

Unless there is some DA-specific restriction involved here, AddRecs (including pointer AddRecs) in SCEV can definitely wrap.


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